Hepatitis B virus (HBV) is a major cause of serious liver diseases, including chronic hepatitis, cirrhosis and hepatocellular carcinoma (HCC) throughout the world and the US, especially among minorities such as African Americans, Native Americans, and Asian Americans. Recent clinical data have pointed to an association between HCC and HBV mutants with in-frame deletions in the preS2 region of the surface gene. We hypothesize that preS2 mutant HBV genomes play a causal role in HBV-associated carcinogenesis, and hence the appearance of these mutants in patients can be used as an early marker for risk of HCC. We will test this hypothesis, by confirming an epidemiological link between preS2 mutants and HCC, and determining if the presence of these mutants can be used as a marker for increased risk of HCC development in patients with chronic hepatitis B. It is anticipated that these experiments will provide direct evidence on the possible utility of preS2 mutants as a marker of HCC risk in chronic hepatitis B, as well as lead in the future to the identification of molecular targets for the prevention and/or therapy of HCC. Hepatitis B virus is a major cause of suffering and death in the world, by causing liver injury, cirrhosis (liver scarring) and, most importantly, liver cancer. Current treatment for liver cancer is inadequate, to a large extent because of our inability to detect the cancer early enough. We hope that our research can lead to the development of new ways for the early detection and hence treatment of liver cancer in these patients. [unreadable] [unreadable] [unreadable]